Someone complained about JSON above, but I think it does a nicer job here:
{
"path": [
[10, 10],
[90, 10],
[90, 90],
[10, 90],
[10, 10]
]
}
No need for the x and y, really. And it's still quite legible on one line. {"path": [[10, 10], [90, 10], [90, 90], [10, 90], [10, 10]]}